Mold, mildew and bacterial contamination are undesirable in consumer goods and on many types of surfaces. Control of such biological contamination has largely been based on the use of biocides. The use of synthetic or natural biocides or derivatives thereof efficiently and in an environmentally acceptable manner is becoming increasingly desirable and necessary.
Metal-ions such as silver, copper and gold ions have been found to possess antimicrobial properties, and compositions including these metal-ions have been used to prevent or inhibit the growth of microorganisms. Metal-ions, metal salts or compositions including these metal ions have been used to prevent the transmetal-ion sequestration of infectious disease and to kill harmful bacteria such as Staphylococcus aureus and Salmonella spp. While metals can be toxic to the microorganisms, they have been found to have an important role in various biological processes at lower concentrations. For example, metal-ions play a crucial role in oxygen transport in living systems, regulate the function of genes and replication in many cellular systems, and are involved in metabolism and enzymatic processes. As a result, the bioavailability of metal-ions in aerobic environments is a major factor in determining the abundance, growth-rate and health of plant, animal and microorganism populations.
Iron is an essential trace element for virtually all living organisms, because iron is an essential component for the proper functioning of many cellular enzymes and proteins. Although iron is one of the most abundant elements in the Earth's crust, it is not readily available for use by living organisms. The bioavailability of iron is limited because compounds of Fe(III), which is the most stable form of iron in air, are insoluble in aerobic environments. As a result, microorganisms use specialized iron uptake mechanisms to obtain this essential element. One such mechanism involves the production of siderophores, such as hydroxamates, catechols or carboxylates, which form water soluble complexes of Fe(III). These Fe(III)-siderophore complexes are then reduced to Fe(II) inside the microorganisms to release the iron for metabolic functions within the microorganisms. Thus, decreasing the bioavailability of iron from an aerobic environment may inhibit the growth of such microorganisms. Several siderophore-antibiotic conjugates have been developed to be used as antibacterial agents. These conjugates compete with the siderophores by selectively chelating with the iron, thereby depriving the microorganism of iron essential for its growth and metabolic activity. However, these conjugates have not been efficient and have not produced promising results in controlling or eradicating microbial contaminations.
Accordingly, there remains a very real and substantial need for antimicrobial compositions capable of effectively controlling and/or inhibiting microbial growth in industrial aqueous systems and in articles of manufacture. Because of increasing environmental regulations, there is still a further need to provide biocidal compositions having enhanced antimicrobial effect which are effective in lower doses than historically used. Use of lower amounts of biocides has a favorable impact on the environment, and allows users to realize significant cost savings. The present invention seeks to fulfill these needs and provides further related advantages.